Along with recent progress in international exchange, an identification card (e.g., ID card, IC card, or passport) that records personal information (particularly an identification card issued by a public agency or a reliable organization) has become increasingly important as an identification means.
Since the September, 2001 spontaneous worldwide multiple terrorist attacks, each country has taken countermeasures such as placing strict controls on entry into and exit from the country. For example, an electronic passport that was standardized by the International Civil Aviation Organization (ICAO) of the United Nations and includes an IC chip into or from which personal information can be written or read, has been introduced. An ID card, an IC card, or the like that records a large amount of information that specifies an individual has also been developed. An identification card (e.g., ID card, IC card, or passport) is normally configured so that personal information (e.g., name, symbols, characters, and photograph) is displayed on the card, sheet, or the like.
Since such an ID card, IC card, or passport specifies an individual, the reliability of the identification card decreases if a third party other than a public agency or a reliable organization can easily falsify or forge the personal information. Such a situation hinders progress in international exchange.
Therefore, it is important to prevent falsification or forging of an identification card such as an electronic passport, an ID card, or an IC card. Specifically, it is important to display a clear image on a small electronic passport, ID card, IC card, or the like with high contrast in order to prevent falsification, forging, or the like.
In view of the above situation, technology of laser marking a name, symbols, characters, photograph, or the like using a laser marking multilayer sheet has attracted attention. For example, Patent Documents 1 and 2 disclose such laser marking technology.
Patent Document 1 aims at providing a laser marking multilayer sheet that is not externally damaged, ensures high contrast, and has excellent surface flatness, and discloses a laser marking multilayer sheet that includes at least (A) a surface layer formed of a transparent thermoplastic resin, and (B) an inner layer formed of a thermoplastic resin composition that includes (b-1) based on 100 parts by weight of a thermoplastic resin, (b-2) 0.01 to 5 parts by weight of a laser beam energy absorber, and (b-3) 0.5 to 7 parts by weight of a coloring agent, the surface layer and the inner layer being formed by a melt coextrusion method.
Patent Document 2 aims at providing a laser marking multilayer sheet that is not externally damaged, ensures high contrast, and has excellent surface flatness and excellent heat resistance, and discloses a laser marking multilayer sheet (first surface layer/inner layer/second surface layer) that includes (A) first and second surface layers formed of a thermoplastic resin composition that includes based on 100 parts by weight of a transparent thermoplastic resin, 0.001 to 5 parts by weight of mica and/or carbon black, and (B) an inner layer formed of a thermoplastic resin composition that includes based on 100 parts by weight of a thermoplastic resin, 0.001 to 3 parts by weight of a laser beam energy absorber, the thickness ratio of the first surface layer, the inner layer, and the second surface layer being 1:4:1 to 1:10:1, and the first surface layer, the inner layer, and the second surface layer being formed by a melt coextrusion method.
The laser marking multilayer sheets disclosed in Patent Documents 1 and 2 exhibit excellent thermal adhesiveness with another laser marking multilayer sheet or a thermoplastic resin sheet (e.g., PETG sheet or ABS resin sheet), and ensure that characters and numerals can be satisfactorily printed by laser marking (i.e., applying a laser beam). However, the laser marking multilayer sheets disclosed in Patent Documents 1 and 2 have a problem in that an image (e.g., face) such as that printed on an identification card (e.g., ID card, IC card, or passport) cannot be necessarily satisfactorily formed. Specifically, it is not sufficiently handled how personal information such as name, symbols, characters and photograph is clearly displayed within narrow dimensions.
Related-Art Document
Patent Document
    Patent Document 1: JP-A-2002-273832    Patent Document 2: Japanese Patent No. 3889431